American John Cook will take a one-shot lead into the final round of the Senior British Open at Royal Troon after shooting a third round four-under-par 67.

Cook took advantage of calmer conditions to equal the lowest round of the week and his six-under-par total of 207 meant he leapfrogged overnight leader Bruce Vaughan.

Vaughan was a shot back at five-under after he recovered from a run of four bogeys around the turn to post a 69.

Argentine Eduardo Romero (68) sat third at four-under.

Holder and three-times British Senior Open winner Tom Watson (71) ended the day in a tie for fourth at one-under par alongside German Bernhard Langer (71).

Australian Greg Norman, equal third in last week's British Open at Royal Birkdale, matched Cook's score to leave him tied for sixth, seven shots of the pace.